Typically, CMOS integrated circuitry has two voltage potentials associated therewith which are known in the art as a supply voltage V.sub.DD and a reference voltage V.sub.SS. The supply voltage V.sub.DD is commonly a more positive voltage than the reference voltage V.sub.SS. For circuit operation where the difference in voltage potential between V.sub.DD and V.sub.SS is approximately eight volts or greater, some processes, such as a silicon gate process, having small device geometries, such as five microns and less, utilize digital logic circuits which may latch-up and maintain false or erroneous data. To overcome this problem, a reduced supply voltage, which is internal to an integrated circuit chip and negative with respect to V.sub.DD, is provided to operate digital logic circuits at a sufficiently low voltage to prevent latch-up. Internal reduced supply voltages previously have been provided by coupling a first terminal of a Zener diode to the supply voltage V.sub.DD and coupling a second terminal of the Zener diode to both a current source and an input of a buffer amplifier. An output of the buffer amplifier provides the reduced internal voltage. A typical Zener diode has a fixed temperature coefficient of approximately +5 millivolt per degree Centigrade.
Others have used series-connected bipolar type diodes which each have a fixed voltage drop of approximately 0.7 volt to provide an internal reduced supply voltage. Size disadvantages are obvious when a substantially reduced voltage is desired because a plurality of diodes must be used. Further, bipolar diodes display a stable negative temperature coefficient of approximately -2 millivolts per degree Centigrade. Others have also coupled a Zener diode in series with a bipolar diode in an attempt to provide a reduced supply voltage displaying a 0 millivolt per degree Centigrade temperature coefficient. These types of internal voltage generators are intended to produce an internal supply voltage that is substantially independent of process and temperature. However, a fixed supply voltage does not compensate devices powered by the power supply (i.e. inverters, NAND gates, etc.) for propagation delay time as a function of process and temperature.